Linguistic comparison allows these languages to be classified into several language families, with little or no discernible affinity to each other. However, the languages of the Caucasus are sometimes mistakenly referred to as a family of languages.

Families indigenous to the Caucasus

Three of these families have no current members outside the Caucasus, and are considered indigenous to the area. The term Caucasian languages is generally restricted to these families, which are spoken by about 11.2 million people.

It is commonly believed that all Caucasian languages have a large number of consonants. While this is certainly true for most members of the Northeast and Northwest Caucasian families (inventories range up to the 80–84 consonants of Ubykh), the consonant inventories of the South Caucasian languages are not nearly as extensive, ranging from 28 (Georgian) to 30 (Laz) – comparable to languages like Russian (up to 37 consonant phonemes, depending on definition), Arabic (28 phonemes), and Western European languages (often more than 20 phonemes).

The autochthonous languages of the Caucasus share some areal features, such as the presence of ejective consonants and a highly agglutinative structure, and, with the sole exception of Mingrelian, all of them exhibit a greater or lesser degree of ergativity. Many of these features are shared with other languages that have been in the Caucasus for a long time, such as Ossetian (which has ejective sounds but no ergativity).

External relations

Since the birth of comparative linguistics in the 19th century, the riddle of the apparently isolated Caucasian language families has attracted the attention of many scholars, who have endeavored to relate them to each other or to languages outside the Caucasus region. The most promising proposals are connections between the Northeast and Northwest Caucasian families and each other or with languages formerly spoken in Anatolia and northern Mesopotamia.

North Caucasian languages

Linguists such as Sergei Starostin see the Northeast (Nakh-Dagestanian) and Northwest (Abkhaz–Adyghe) families as related and propose uniting them in a single North Caucasian family, sometimes called Caucasic or simply Caucasian. This theory excludes the South Caucasian languages, thereby proposing two indigenous language families. While these two families share many similarities, their morphological structure, with many morphemes consisting of a single consonant, make comparison between them unusually difficult, and it has not been possible to establish a genetic relationship with any certainty.

Ibero-Caucasian languages

There are no known affinities between the South Caucasian and North Caucasian families. Nevertheless, some scholars have proposed the single name Ibero-Caucasian for all the Caucasian language families, North and South, in an attempt to unify the Caucasian languages under one family.